Analysis of the effects of xenon oscillation on reactor power

Abstract

Xenon oscillation is an important phenomena at nuclear power plants with great built-in power capacity. In this mechanism the concentration of the xenon nuclei is changing significantly and not evenly depending on time and space during the chain reaction. As the xenon-135 isotope has a remarkable absorption cross section in the thermal zone, it is crucial to take into account its change throughout the whole lifetime of the reactor. Nowadays most of the planned and constructed nuclear power plants have a high built in capacity and an extended reactor zone which means that xenon oscillation is a real I&C problem of the nuclear energy sector. A great example of these kind of investments is the Hungarian Paks II project in which 2 blocks with 1200 MW capacity each are going to be constructed. As a conclusion for granting nuclear safety it is crucial to be able to simulate the processes concerning the xenon isotopes during the reactor lifetime. The main goal of the research is to simulate precisely the change of the xenon concentration and the phenomenon of xenon oscillation in time and place and to create an algorithm which is able to compensate the change of the output power due to xenon oscillation. The applied model is the one- dimensional diffusion equation coupled with the equations regarding the concentration of xenon and iodine isotopes. In the work finite differences method is used to solve this nonlinear differential equation system in Matlab.